Currently known conveyor belts, particularly the ones used in the food industry, are generally constituted by two or more parallel chains, which are connected transversely by rod-like elements.
The ends of said rod-like elements are fixed to the corresponding and mutually opposite links of said chains.
Transport means, suitable to move the chains of the conveyor belt in a chosen travel direction, and means for recovering any elongation of said belt are associated with said chain-type conveyor belts and are rigidly coupled to a travel frame for the belt.
The transport means are generally constituted by motorized gears, the teeth of which engage the links of the adjacent chains.
The means for recovering the elongation of the belt start to operate when the belt slows down or accelerates in one of its parts, tensioning the adjacent belt portions.
The belt, which generally has a certain elasticity, is elongated by being thus stressed, and can also elongate due to any unevenness in the pitch of the gears or links, due to temperature variations, due to intervening wear of the chains or gears, and other similar drawbacks.
Excessive elongation, however, can cause the belt to break or cause a plastic deformation that makes it defective and unusable.
Excessive tension of the belt, further, can displace the products being conveyed from the correct conveyance position, with the risk of compromising the subsequent operations of the process (such as for example packing, cartoning and the like) to which said products are subjected.
In currently known conveyor belts, the frame supports the transport means on a straight portion and the belt elongation recovery means in the curved regions that are typical for example of spiral belts.
These known elongation recovery means are constituted by curved guides having an elastically variable radius.
The tension of the belt causes the internal part of the elastic curve, stressed by said belt, to shorten its radius, thus discharging the tensions that are accumulating on the belt.
These elastic curves have a relatively complicated structure that is expensive to provide.
Said elastic curves in fact must be custom-designed for each conveyor belt supporting frame, and as such they must be manufactured in small-batches, with consequent substantial production costs.